Hereditary hyperferritinemia cataract syndrome: clinical, genetic, and laboratory findings in 5 families

Hereditary hyperferritinaemia-cataract syndrome (HHCS) – an underestimated condition: ferritin light chain variant spectrum in German families

Background

In hereditary hyperferritinaemia-cataract syndrome (HHCS), single nucleic acid alterations in the ferritin light chain (L-ferritin) iron response element (IRE) constitutively derepress ferritin synthesis, resulting in hyperferritinaemia, L-ferritin deposits in the lens of the eye and early bilateral cataract onset.

Methods

In this study, six German families with putative HHCS were analysed. Clinical diagnosis of HHCS was based on medical history, evaluation of ferritin serum levels, transferrin saturation and clinical ophthalmological examination. Diagnosis was confirmed by polymerase chain reaction (PCR)-based DNA sequencing of the L-ferritin IRE.

Results

Genetic analysis of the L-ferritin IRE revealed relevant single nucleic acid alterations in each of the affected families. Variants c.-168G > A, c.-168G > U and c.-167C > U were located in the C-bulge region; and variants c.-161C > U and c.-157G > A were located in the hexanucleotide loop of the L-ferritin IRE.

Conclusions

Family history of hyperferritinaemia and juvenile cataracts are strong indicators of HHCS. Genetic analysis of the L-ferritin IRE is a straightforward procedure to confirm the diagnosis. Accurate diagnosis of hyperferritinaemia can avoid unnecessary treatment by venesection, and focus attention on early cataract detection in offspring at risk.

High-Throughput Genetic Screening of 51 Pediatric Cataract Genes Identifies Causative Mutations in Inherited Pediatric Cataract in South Eastern Australia

Pediatric cataract is a leading cause of childhood blindness. This study aimed to determine the genetic cause of pediatric cataract in Australian families by screening known disease-associated genes using massively parallel sequencing technology. We sequenced 51 previously reported pediatric cataract genes in 33 affected individuals with a family history (cases with previously known or published mutations were excluded) using the Ion Torrent Personal Genome Machine. Variants were prioritized for validation if they were predicted to alter the protein sequence and were absent or rare with minor allele frequency <1% in public databases. Confirmed mutations were assessed for segregation with the phenotype in all available family members. All identified novel or previously reported cataract-causing mutations were screened in 326 unrelated Australian controls. We detected 11 novel mutations in GJA3, GJA8, CRYAA, CRYBB2, CRYGS, CRYGA, GCNT2, CRYGA, and MIP; and three previously reported cataract-causing mutations in GJA8, CRYAA, and CRYBB2 The most commonly mutated genes were those coding for gap junctions and crystallin proteins. Including previous reports of pediatric cataract-associated mutations in our Australian cohort, known genes account for >60% of familial pediatric cataract in Australia, indicating that still more causative genes remain to be identified.

Novel missense mutation in the bZIP transcription factor, MAF, associated with congenital cataract, developmental delay, seizures and hearing loss (Aymé-Gripp syndrome)

Background

Cataract is a major cause of severe visual impairment in childhood. The purpose of this study was to determine the genetic cause of syndromic congenital cataract in an Australian mother and son.

Method

Fifty-one genes associated with congenital cataract were sequenced in the proband using a custom Ampliseq library on the Ion Torrent Personal Genome Machine (PGM). Reads were aligned against the human genome (hg19) and variants were annotated. Variants were prioritised for validation by Sanger sequencing if they were novel, rare or previously reported to be associated with paediatric cataract and were predicted to be protein changing. Variants were assessed for segregation with the phenotype in the affected mother.

Result

A novel likely pathogenic variant was identified in the transactivation domain of the MAF gene (c.176C > G, p.(Pro59Arg)) in the proband and his affected mother., but was absent in 326 unrelated controls and absent from public variant databases.

Conclusion

The MAF variant is the likely cause of the congenital cataract, Asperger syndrome, seizures, hearing loss and facial characteristics in the proband, providinga diagnosis of Aymé-Gripp syndrome for the family.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0414-7) contains supplementary material, which is available to authorized users.

Recurrent mutation in the crystallin alpha A gene associated with inherited paediatric cataract

Background

Cataract is a major cause of childhood blindness worldwide. The purpose of this study was to determine the genetic cause of paediatric cataract in a South Australian family with a bilateral lamellar paediatric cataract displaying variable phenotypes.

Case presentation

Fifty-one genes implicated in congenital cataract in human or mouse were sequenced in an affected individual from an Australian (Caucasian) family using a custom Ampliseq library on the Ion Torrent Personal Genome Machine. Reads were mapped against the human genome (hg19) and variants called with the Torrent Suite software. Variants were annotated to dbSNP 137 using Ion Reporter (IR 1.6.2) and were prioritised for validation if they were novel or rare and were predicted to be protein changing. We identified a previously reported oligomerization disrupting mutation, c.62G > A (p.R21Q), in the Crystallin alpha A (CRYAA) gene segregating in this three generation family. No other novel or rare coding mutations were detected in the known cataract genes sequenced. Microsatellite markers were used to compare the haplotypes between the family reported here and a previously published family with the same segregating mutation. Haplotype analysis indicated a potential common ancestry between the two South Australian families with this mutation. The work strengthens the genotype-phenotype correlations between this functional mutation in the crystallin alpha A (CRYAA) gene and paediatric cataract.

Conclusion

The p.R21Q mutation is the most likely cause of paediatric cataract in this family. The recurrence of this mutation in paediatric cataract families is likely due to a familial relationship.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-1890-0) contains supplementary material, which is available to authorized users.